Adaptation to high pressure; insights from the genome of an evolved Escherichia coli strain with increased piezotolerance

Pressure is a key environmental parameter that influences the activity and distribution of microbial life on our planet. Despite its key role there is still not a definitive list of essential genes for microbial adaptation to life under increasing pressure. In this study we used a previously characterized Escherichia coli strain (AN62) evolved to grow at pressure (60 MPa) non-permissive to the parental strain and performed comparative genomics in order to identify the genome-level adaptations that might allowed the observed pressure-adapted phenotype. We identified 18 mutations in total of which 3 mutations were present in both the parental and evolved strain, 3 mutations were only present in the parental strain, and 12 mutations were observed only in the evolved AN62 strain. Among the characterized mutations we observed a point mutation in the acyl carrier protein (acpPV43G). Complementation experiments revealed that the observed V43G mutation in AcpP is responsible for increased levels of cis-vaccenic acid but is not alone responsible for the pressure adapted phenotype. Further molecular dynamics and docking simulations suggested that the V43G mutation promoted stronger binding of the AcpP protein to partner enzymes of the fatty acid biosynthesis pathway involved in fatty acid unsaturation.